Effects of O2 and H2O in the Oxidative Steam-Reforming Reaction of Ethanol on Rh Catalysts

• Published in: Journal of physical chemistry. C Vol. 123; no. 18; pp. 11649 - 11661
• Main Authors: Hsia, Yu-Yao, Huang, Yi-Cheng, Zheng, Hong-Sheng, Lai, Yu-Ling, Hsu, Yao-Jane, Luo, Meng-Fan, Wang, Jeng-Han
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.05.2019
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b00747

With both real-world catalyst Rh/CeO2 and model-system Rh(111), we investigated how oxygen and water play effective roles in the oxidative steam-reforming (OSR) reaction of ethanol. The results show that atomic oxygen (O*) on Rh surfaces enhanced significantly the decomposition probability of ethanol and altered the reaction path from one via cleavage of the C–Hβ bond forming an oxametallacycle to another via cleavage of the C–Hα bond forming an acetaldehyde; this alternation highly promoted the production of H2, along with side products CO, CH4, and H2O. The reaction path shifted to acetate intermediates with the oxygen content greater than 0.08 ML, which suppressed the production of H2 but promoted that of CO2. The effect of hydroxyl (OH*) resembled that of O*, whereas OH* further enhanced the reaction probability of ethanol on Rh surfaces precovered with O* but slightly affected the reaction path. The intermolecular hydrogen bonding between surface O* or OH* and ethanol or its fragments accounts for the enhanced reaction probability and the altered reaction path. The mechanistic results yield clues for a rational optimization of the OSR reaction of ethanol, through tuning the quantities of O2 and H2O, the production of H2, and less poisoning carbon species.